This invention relates in general to optical oximeters and relates more particularly to an adapter that enables an optical oximeter probe, that is designed/configured to be utilized on an associated oximeter monitor, to be used on a different oximeter monitor that utilizes a different probe configuration.
Because of the importance of oxygen for healthy human metabolism, it is important to be able to measure the oxygen content of a patient's blood. The monitoring of a patient's arterial hemoglobin oxygen saturation during and after surgery is particularly critical.
Non-invasive oximeters have been developed that direct light through a patient's skin into a region, such as a finger, containing arterial blood. This light typically contains two or more primary wavelengths of light. Examples of such oximeters are disclosed in U.S. Pat. No. 5,209,230 entitled "Adhesive Pulse Oximeter Sensor With Reusable Portion" issued to Swedlow, et al. and in U.S. Pat. No. 4,700,708 entitled "Calibrated Optical Oximeter Probe" issued to New, Jr. et al., both assigned to the assignee of the present invention, the disclosures of which are incorporated herein by reference. The oximeter in the patent by New, Jr. et al. includes a probe that contains a resistor having a resistance that can be measured by a monitor to which the probe is attached. The measured value of this resistance is indicative of the wavelengths of the light directed from the light emitting diodes (LEDs) through the patient's epidermis. The monitor uses this information and the measured intensities of light detected at those wavelengths to calculate the blood arterial oxygen content of the patient. The LEDs are activated in non-overlapping temporal intervals, so that the amount of absorption of light at each of these two wavelengths is measured separately.
Optical probes can be electrically configured in a plurality of ways. U.S. Pat. No. 5,249,576 entitled "Universal Pulse Oximeter Probe" issued to Goldberger, et al., illustrates two configurations of a red light emitting diode (LED) and an infrared LED that emit light into a patient's finger. These two prior art configurations are illustrated in FIGS. 1 and 2. FIG. 1 shows a probe configuration 10 in which a pair of LEDs 11 and 12 are connected in a "3-lead configuration" 13 in which the two LED anodes are connected to a terminal 14 and in which the two LED cathodes are each connected to uniquely associated leads 15 and 16. This probe also includes: a photodetector 17 that detects light emitted from LEDs 11 and 12; and a resistor 18 having a resistance which is indicative of the wavelength of light produced by at least one of LEDs 11 and 12 (alternately, the resistance can indicate other or additional parameters). A probe having a 3-lead configuration of LEDs will be referred to herein as a "3-lead probe" 10. The leads to the LEDs 14, 16, and 15 are indicated as ground, VO1, and VO2, respectively. The VO1 and VO2 designations indicate these are the first and second LED drive voltage leads for oximeters made by other than Nellcor, the assignee of this application. The "O" in the VO1 and VO2 terms is intended to refer to "other." Thus, this probe is sometimes referred to as an "other probe."
In a second embodiment, shown in FIG. 2, two LEDs 21 and 22 are connected in a "2-lead configuration" 23 in which the anode of first LED 21 and the cathode of a second LED 22 are connected to a first lead 24, and the cathode of the first LED 21 and the anode of the second LED 22 are connected to a second lead 25. This probe also includes a photodetector 26 and a resistor 27 (or other type of mechanism which is indicative of the wavelength produced by one or both LEDs, and/or other parameters). A probe having a 2-lead configuration of LEDs will be referred to herein as a "2-lead probe 20". The leads to the LEDs are indicated as VN1, and VN2, corresponding to the Nellcor probe first and second voltage signals. This type of probe is also sometimes referred to as a "Nellcor probe."
An oximeter monitor that is designed to utilize a probe having the 2-lead configuration of LEDs will be referred to herein as an "2-lead monitor" or "Nellcor oximeter monitor." Similarly, an oximeter monitor that is designed to utilize a probe having the 3-lead configuration of LEDs will be referred to herein as a "3-lead monitor" or "other oximeter monitor."
Some oximeter probes may use one or more additional LEDs. For instance, a second red LED is sometimes used in combination with the first red LED to achieve more balanced light levels.
For either of the above two configurations of FIGS. 1 and 2, power is applied to the two LEDs in a manner such that only one of them is activated at any given time, so that, at any given time, the output signal from the detector is produced in response to light from at most one of these two LEDs. This simplifies calculations needed to convert detected light intensities into an indication of the oxygen concentration in a patient's blood.
The incompatibility between different types of probes and different types of oximeters significantly increases the cost of supplying probes for both types of oximeters. In particular, for the manufacturer of such probes, not only is there the cost of designing multiple different types of probes, there is also the cost of building multiple different manufacturing lines, purchasing components for multiple different manufacturing lines, sorting components for multiple different manufacturing lines and selling multiple different types of probes. In addition, the manufacturing and distribution costs of each different type of probe do not benefit as much from the economies of scale associated with the increased product volume that would occur if there were only one type of probe. The total cost of these probes also includes the indirect costs incurred by hospitals that use both types of probes so that such hospitals also bear the increased costs associated with the smaller volume orders of each type of probe, the cost of stocking multiple different types of probes and the costs of interacting with multiple vendors. All of these factors significantly increase the cost of monitoring patient oxygen saturation.
The Goldberger patent discussed above addresses this problem by presenting a probe that can be configured to work with any oximeter. The photodetector and light sources within this probe are mounted without any interconnections, and a cable interconnects these elements into various configurations by means of appropriately inserted jumper leads. Unfortunately, although this structure enables this probe to be adapted for a wide variety of oximeters, it does not allow any way for a probe which already has its electrical elements interconnected to be used with any arbitrarily selected oximeter.
It is an object of the invention to provide an adapter that can be connected between a probe that has its electrical elements interconnected in a first configuration and a monitor designed for use with a probe having a second electrical interconnect configuration such that this probe and this monitor will function properly with one another.